USA 3G sunset - swapping SIM could create headache

[Rick Law]

Arrgh...  In the USA, both T-Mobile and AT&T are beginning to sunset their 3G.

If you are still using 3G phone, don't swap SIM around...  I ran into this problem so I'm alerting others to expect possible problem with SIM swapping.

AT&T (my regular network, 3G shutdown is scheduled for Feb 2022)

I was expecting a call but my regular (3G) phone was on low-battery.  So, I put the SIM into another phone (4G/LTE) to catch the calls while my regular phone is being charged.  Re-inserting the SIM back to my now fully-charged 3G phone, everything looked normal, address bar is full and shows I am connected to AT&T network...  It looked so normal and typical I didn't even check - but it actually is not working.  I didn't even realize it was not working until I got an email: "...I've been calling you for a couple of days and your phone is not working..."  I checked: it can't receive and it can't make calls while externally everything looked normal.  It took a call to AT&T to re-enable my regular 3G phone.

T-Mobile (Business customer is scheduled for Dec 2021, unknown for consumer lines)

Since I didn't particularly like my AT&T's plan, I got a T-Mobile prepaid to check coverage in my area prior to AT&T shut down my 3G phone.  The T-Mobile's SIM worked just fine on my 4G/LTE phone.  I inserted the SIM into my regular 3G to copy some numbers then re-inserting it to the 4G/LTE phone.  Now it wont connect.  Just like before with AT&T, the phone shows full 5 bars and I am on the T-Mobile network, but it actually is not working.  After two calls to tech-support, I did got the T-Mobile SIM re-enabled on my 4G/LTE test phone.

Later, I thought about the reason why the 4G/LTE phone isn't working when they are merely shutting down 3G.  It may be my 4G/LTE phone doesn't support VoLTE and so it would be 3G voice-wise, may be.

So, if the SIM card is switched between phones, be mindful you may run into problems re-inserting back to originally working phone...

[firehopper]

my dad is on consumer cellular, and had 3g phone, his 3g phone was set to go dead on june 30th so he had to spend $35 to get a 4g version of the same flip phone.. was a pain in the arse to setup, as I hate t9 keyboards!

[Rick Law]

I expected that the phones will stop working sooner or later since their schedule was set, that was not the surprise.  What caught me off-guard was: pulling the SIM from my working (compliant till sometime in 2022) phone and insert it into another phone (compliant till sometime in 2022) stops the SIM from working again -- even when placed back into the phone that was working with the SIM moments ago.

This is different than what happened during the moved from 2G->3G.  I was swapping SIMs back and forth a lot while shopping for replacements phones.  The SIMs continue to function swapping back and forth during replacement shopping, and during migration.

That I cannot swap SIM back and forth added just a minor inconvenient.  That it caught me off-guard was the major annoyance.  The need to fight with robo-phone support multiple times first, then gained the opportunity to explain the issue to a real support person (who doesn't always get it), then needing to drive back to the phone store for a new SIM (which was unnecessary - on second failure, I caught on what was wrong and was able to get them to clear the SIM registration rather than driving back to the store for another SIM). 

No one likes fighting with Robo-Phone-Support.  That is why I wrote this post, part ranting, and part print out an "aviod this" sign.

[SteveyG]

3G needs some fairly legacy equipment which is probably running out of support. I'd be surprised if there is a large percentage of users that will be affected by this, other than maybe embedded systems or monitoring systems for alarms etc

What's with this recent use of the term "sunset" Strange one.

[rsjsouza]

My theory is that the transition between 2G to 3G was smoother/slower as the majority of people offered more resistance to throw away their older phones - nowadays these folks will be outliars in comparison with the overall customer base. Also, internet access probably comprises a much more significant portion of the phone activities itself, thus the move to a newer/faster packet technology would be more palatable.

But I agree the SIM dance is completely stupid.

What's with this recent use of the term "sunset" Strange one.

I have been hearing this word used in this sense for about twenty years. It is just one more way of saying a cold hard truth in a soft way so as to not hurt the feelings of whomever is on the other side of the conversation. 

This video comes to mind:

[SteveyG]

What's with this recent use of the term "sunset" Strange one.

I have been hearing this word used in this sense for about twenty years. It is just one more way of saying a cold hard truth in a soft way so as to not hurt the feelings of whomever is on the other side of the conversation. 

The sun rises again though the next day...  Surely phasing out or retiring is more applicable.

[themadhippy]

Are you sure it aint some sort of" security feature"  i recall having a similar issue years ago and it just  required a code provided with the sim being entered into the phone.

[SiliconWizard]

Are you sure it aint some sort of" security feature"  i recall having a similar issue years ago and it just  required a code provided with the sim being entered into the phone.

I would think that as well.

[tooki]

I think this also exemplifies a few things, including the complexity of SIM cards (which aren’t just dumb storage devices, nor even “just” encryption processors: they’re full application processors that run carrier applications), and that the network itself has complexity we don’t see.

[SiliconWizard]

I think this also exemplifies a few things, including the complexity of SIM cards (which aren’t just dumb storage devices, nor even “just” encryption processors: they’re full application processors that run carrier applications), and that the network itself has complexity we don’t see.

Speaking of which, there are now phones and networks that can operate without a physical SIM card. That's called eSIM. It's a virtual SIM card running on the processor, and it embeds much more information than traditional SIM cards as far as I've understood. eSIM is probably going to replace SIM cards completely.

[Rick Law]

In my opinion, eSIM rather missed the point of having a SIM at all.

Before this 4G era, the SIM is the portable "personality card" for your phone.  Inserting that card into a phone and that phone instantly becomes your phone.

Twice I dropped my phone in water.  I just wiped the SIM clean, put it in another phone and off I go - another phone with my phone number and contact list.  eSIM (non-portable) would remove that portability.

Decades ago (early 2G era) after my first business trip to Europe, I got off Verizon (CDMA, no SIM so it was eSIM of that era) and migrated to AT&T (2nd line T-Mobile) for the flexibility of GSM SIM-portability.  Subsequent trips I have my unlocked GSM phone.  I can use any GSM carrier's SIM on the same phone.  While overseas, I can also use a local-SIM and make local calls rather than via my USA-carrier.  Same physical phone with many personalities suitable for the occasion.

That said, 4G/LTE (to be precise, VoLTE, aka HD-Voice) will make cross-carrier portability difficult.  Unconfirmed but as I understand it: VoLTE on AT&T and T-Mobile are not the same.  So "carrier unlocked phone" may no longer ensure it will work on both AT&T and T-Mobile anymore.

[chickenHeadKnob]

What's with this recent use of the term "sunset" Strange one.

I have been hearing this word used in this sense for about twenty years. It is just one more way of saying a cold hard truth in a soft way so as to not hurt the feelings of whomever is on the other side of the conversation. 

The sun rises again though the next day...  Surely phasing out or retiring is more applicable.

I'm old, as in sixty+. I encountered "sunset clause" as legal jargon concerning contracts going back more than 40 years. It is nothing new and has nothing to do with fee-feels you may be having.

[tooki]

I think this also exemplifies a few things, including the complexity of SIM cards (which aren’t just dumb storage devices, nor even “just” encryption processors: they’re full application processors that run carrier applications), and that the network itself has complexity we don’t see.

Speaking of which, there are now phones and networks that can operate without a physical SIM card. That's called eSIM. It's a virtual SIM card running on the processor, and it embeds much more information than traditional SIM cards as far as I've understood. eSIM is probably going to replace SIM cards completely.

Yep, though as far as I know, it’s actually a dedicated embedded processor, since it is responsible for network security.

[tooki]

In my opinion, eSIM rather missed the point of having a SIM at all.

Before this 4G era, the SIM is the portable "personality card" for your phone.  Inserting that card into a phone and that phone instantly becomes your phone.

Well, it still is, both in the 4G and 5G eras, for the vast majority of users.

That said, 4G/LTE (to be precise, VoLTE, aka HD-Voice) will make cross-carrier portability difficult.  Unconfirmed but as I understand it: VoLTE on AT&T and T-Mobile are not the same.  So "carrier unlocked phone" may no longer ensure it will work on both AT&T and T-Mobile anymore.

Whoa there. You’re confounding multiple things. VoLTE ≠ HD Voice. Higher-bandwidth voice calling exists on 3G and even 2G networks, too. The specific implementation called “HD Voice” requires VoLTE, but not all VoLTE carriers and phones support it. And many carriers do not support high-bandwidth calls to other carriers, even if they use the same standard.

As for carrier locking: most carriers stopped that nonsense anyway, but HD voice support has NOTHING to do with this. The phones support what they support, the carriers support what they support, and the carriers’ peering support varies, so you end up with whatever the weakest link is for a given call.


EDIT: Closer inspection reveals that the "HD Voice" trademark specifically requires the use of the AMR-WB codec, but it can be implemented on any network type, not just VoLTE.

[Rick Law]

...
...

That said, 4G/LTE (to be precise, VoLTE, aka HD-Voice) will make cross-carrier portability difficult.  Unconfirmed but as I understand it: VoLTE on AT&T and T-Mobile are not the same.  So "carrier unlocked phone" may no longer ensure it will work on both AT&T and T-Mobile anymore.

Whoa there. You’re confounding multiple things. VoLTE ≠ HD Voice. Higher-bandwidth voice calling exists on 3G and even 2G networks, too. The specific implementation called “HD Voice” requires VoLTE, but not all VoLTE carriers and phones support it. And many carriers do not support high-bandwidth calls to other carriers, even if they use the same standard.

As for carrier locking: most carriers stopped that nonsense anyway, but HD voice support has NOTHING to do with this. The phones support what they support, the carriers support what they support, and the carriers’ peering support varies, so you end up with whatever the weakest link is for a given call.

You are right, I should not have put it as "VoLTE aka HD Voice".

As to carrier-lock on phones, most US carriers are still locking phones, but they hardly offer the discounts they used to anymore.  With "HD voice" implementation differing from carrier to carrier, an unlocked phone would need to support most major carriers' implementation, otherwise the phone wont work.  That makes shopping for unlocked phone a bit more complicated: not just the right frequencies support, now one more factor that must be compatible.

[tooki]

As to carrier-lock on phones, most US carriers are still locking phones, but they hardly offer the discounts they used to anymore. 

Still?!? 

With "HD voice" implementation differing from carrier to carrier, an unlocked phone would need to support most major carriers' implementation, otherwise the phone wont work.  That makes shopping for unlocked phone a bit more complicated: not just the right frequencies support, now one more factor that must be compatible.

You're still confounding things. Again, "HD Voice" is not a generic descriptor, but the name of a specific standard. (Wiki:Wideband audio says: 'In cellular communication, "HD Voice" specifically refers to AMR-WB (G.722.2) in VoLTE. It is a trademark of GSMA, who runs a certification program around the logo.') There are no carrier-specific implementations. What is happening is the carriers beginning to require HD Voice support in the handsets. The differences in cutoff dates (and sloppiness in maintaining lists of devices that support it) is what's probably making you think it's carrier-specific.

[Rick Law]

As to carrier-lock on phones, most US carriers are still locking phones, but they hardly offer the discounts they used to anymore. 

Still?!? 

Yeah, AT&T and T-Mobile phones are not interchangeable unless you get the carrier unlocked kind.  Verizon is of course an island by itself.  The discount they offer is little to none, but the locking is still there.  The "discount" these days is installment - you can pay $X for Y months which adds up to pretty much the same as buying the phone outright.

...
You're still confounding things. Again, "HD Voice" is not a generic descriptor, but the name of a specific standard. (Wiki:Wideband audio says: 'In cellular communication, "HD Voice" specifically refers to AMR-WB (G.722.2) in VoLTE. It is a trademark of GSMA, who runs a certification program around the logo.') There are no carrier-specific implementations. What is happening is the carriers beginning to require HD Voice support in the handsets. The differences in cutoff dates (and sloppiness in maintaining lists of devices that support it) is what's probably making you think it's carrier-specific.

I probably am using the wrong descriptor.  To me, it doesn't matter what they call it - their voice implementation is different causing incompatibility that prevents even unlocked phone to work across carriers is the issue,  at least as reported in magazine/web-articles.

Granted, there are higher end phones (Apple, Samsung, etc.) that will work across carriers.  I am referring to the generic economic carrier-unlocked phones.

It is just a damn phone.  As long as someone can call me, and I can call someone, I am happy with it.  I could do that easily with 2G.  Get on ebay or whatever, order an unlocked phone, insert my SIM in it and off I go.

After days of research, I gave up the hunt - I'm waiting for a flip-phone shipment from AT&T, and separate flip-phone for T-Mobile is also en-route.  I may yet get them unlocked to try, but right now I am just testing coverage and decide which carrier I want to go with.  Now that I am not doing international business travel anymore, lacking the ability to use a local SIM is not a critical issue for me anymore.  Having experienced at home I had only T-Mobile, and at work I had only AT&T/Cingular; I know they both have grown a lot since but I still like to test their coverage within the area I frequent prior to deciding which one I want to go with. 

[AntiProtonBoy]

What's with this recent use of the term "sunset" Strange one.

I have been hearing this word used in this sense for about twenty years. It is just one more way of saying a cold hard truth in a soft way so as to not hurt the feelings of whomever is on the other side of the conversation. 

I think industry just love to use wanky catch phrases like that, just like "the chickens have come home to roost".

[retiredfeline]

Sunset clause is a phrase that has been in legal use for decades, and chickens coming home to roost is even older, from the time of Chaucer.

Not all terms are invented by marketing. If there is a phrase circulating that captures the concept succinctly then people will adopt it.

[ThermallyFrigid]

In my opinion, eSIM rather missed the point of having a SIM at all.

Before this 4G era, the SIM is the portable "personality card" for your phone.  Inserting that card into a phone and that phone instantly becomes your phone.

Twice I dropped my phone in water.  I just wiped the SIM clean, put it in another phone and off I go - another phone with my phone number and contact list.  eSIM (non-portable) would remove that portability.

Decades ago (early 2G era) after my first business trip to Europe, I got off Verizon (CDMA, no SIM so it was eSIM of that era) and migrated to AT&T (2nd line T-Mobile) for the flexibility of GSM SIM-portability.  Subsequent trips I have my unlocked GSM phone.  I can use any GSM carrier's SIM on the same phone.  While overseas, I can also use a local-SIM and make local calls rather than via my USA-carrier.  Same physical phone with many personalities suitable for the occasion.

That said, 4G/LTE (to be precise, VoLTE, aka HD-Voice) will make cross-carrier portability difficult.  Unconfirmed but as I understand it: VoLTE on AT&T and T-Mobile are not the same.  So "carrier unlocked phone" may no longer ensure it will work on both AT&T and T-Mobile anymore.

I was told that......
The ability to track you and every use of the phone has become a priority far more important than user convenience.  The Chinese people have absolutely zero expectation of privacy so there it's a non issue.

Was that incorrect?

[SiliconWizard]

In my opinion, eSIM rather missed the point of having a SIM at all.

Before this 4G era, the SIM is the portable "personality card" for your phone.  Inserting that card into a phone and that phone instantly becomes your phone.

I agree. But it gives more control to the operators, making you completely dependent on them for portability.

The customer was once king. These days are long gone.

[Rick Law]

Yeah, the good old days of just a simple phone are gone...  I just want a simple voice-only phone, but even the new flip phones has all that damn junk loaded on it, none for my benefit but theirs...

I really do miss those good old days.

[tooki]

In my opinion, eSIM rather missed the point of having a SIM at all.

Before this 4G era, the SIM is the portable "personality card" for your phone.  Inserting that card into a phone and that phone instantly becomes your phone.

I agree. But it gives more control to the operators, making you completely dependent on them for portability.

The customer was once king. These days are long gone.

LOL what? That’s the exact opposite of how things went. We used to be far MORE carrier-dependent than we are now.

Have you forgotten that for most of the history of telephony in most places, there was a single national monopolist for phone service? The customer was certainly not “king”.

[Rick Law]

SIM vs eSIM (or no SIM) really is just half the equation.  SIM doesn't free the customer from carrier, however, it unlink the lock between the carrier and the phone hardware.  So one is tied to the carrier up-to but excluding the end point.

If I have carrier X's SIM, I can use that on any compatible phone.  So my phone choice is carrier independent.  However, eSIM (or no SIM) likely ties the phone hardware to the carrier and a specific phone.  So one is tied to the carrier up-to and including the end point.

I said "...likely ties the phone..." above because one can of course implement eSIM in such a way that it can be moved between phones, but I doubt that would be the typical implementation.  Besides, you have to "export" that eSIM first before you can use it on a different phone.  If the reason is because your phone took a bath at the beach and wont power up, you are as lost as no-SIM.

[tooki]

I don’t disagree that the eSIM is less portable than a hardware SIM. But I was responding to the preposterous claim that “the customer was once king”.

Have you guys all forgotten what the pre-iPhone days of mobile carriers were like, in particular in USA? ATT (the old one on TDMA), Sprint and Verizon used nearly-proprietary hardware. (And remember Nextel, which literally used an entire proprietary mobile network standard?) Cingular and T-Mo were already GSM but locked down everything. Every carrier loaded custom firmware onto their devices to plaster their proprietary BS apps everywhere, defacing even excellent hardware. (I had an otherwise lovely Sony-Ericsson phone that Cingular had stolen two useful buttons from, hard-mapping them to useless carrier apps instead of the useful functions those buttons normally had.)

Then Apple came along and convinced Cingular to agree to have zero control over the handset software and apps. I cannot overstate enough how much of a game changer this was. And then all the other carriers had to agree to the same thing because they wanted to sell the iPhone, too. The entire smartphone industry benefited immensely from Apple dedtroying the carriers’ stronghold on handset software. Apple is the company that turned the carriers into the “dumb pipes” they should be.

[Rick Law]

...
Have you guys all forgotten what the pre-iPhone days of mobile carriers were like, in particular in USA? ATT (the old one on TDMA), Sprint and Verizon used nearly-proprietary hardware. (And remember Nextel, which literally used an entire proprietary mobile network standard?) Cingular and T-Mo were already GSM but locked down everything. Every carrier loaded custom firmware onto their devices to plaster their proprietary BS apps everywhere, defacing even excellent hardware. (I had an otherwise lovely Sony-Ericsson phone that Cingular had stolen two useful buttons from, hard-mapping them to useless carrier apps instead of the useful functions those buttons normally had.)

Then Apple came along and convinced Cingular to agree to have zero control over the handset software and apps. I cannot overstate enough how much of a game changer this was. And then all the other carriers had to agree to the same thing because they wanted to sell the iPhone, too. The entire smartphone industry benefited immensely from Apple dedtroying the carriers’ stronghold on handset software. Apple is the company that turned the carriers into the “dumb pipes” they should be.

Our recollection is not the same, perhaps because regional/national differences.  I don't recall Apple being influential to the phone market at all in the early days.

At the time Cingular was Cingular (early 2000, Cingular not yet acquired by AT&T), I needed both T-Mobile and Cingular as my regular carrier.  I had coverage with T-Mobile at home (and no Cingular), and Cingular at work (but no T-Mobile).  I had T-Mobile cheap flip phone that was unlocked and can use Cingular and other alien SIMs.  It was also very simple to get Cingular phones unlocked to use T-Mobile and other alien SIM also.  So those phones were entirely carrier independent, I used them in the USA, Europe, and Asia.  The carrier has nothing to say about it and they had no control over it.  For a carrier branded phone, they can refuse to give you the unlock code, but you can always get a phone (like the Moto Razr) that is factory unlocked.

Then in 2004, I switch over to Treo 650.  I have factory-unlocked ones that swap SIMs (T-Mobile, Cingular, other alien SIMs) without distinction.  It just works.  I have unlocked Cingular-branded Treo 650 and they can use alien SIM without distinction.  I later "debranded" the Cingular Treo 650 to run pure Treo 650 firmware also without problem.  The only Cingular thing about them (after debranding) was just the different color scheme the phone have (Cingular ones are lighter grey and a Cingular label metallic color frame around the TFT screen).  Again, entirely carrier independent.  I even have an after market dual-SIM kit that allowed you to cut your two SIMs and fit it into the same SIM tray - but both SIMs are not active at the same time, you select which SIM to use with a Treo 650 App that came with the kit.

That was way before Apple even got into the phone market. Apple iPhone 1 was introduced in 2007.

I was addicted to debranding.  I was still using my Treo as my main phone, but I have my two Zenfone 2e (AT&T only) phones unlocked (not factory unlocked, but with unlock code) and debranded so they run ASUS software with nothing AT&T there.  They are like Asus Zenfone 2 (ZE500CL) but with less memory.  I ended up sticking with my Treo650 until carriers moved to sunset 2G/2.5G phones to 3G only.

So, carrier has no control with factory unlocked phones prior to Apple even got into the market.  They had no influence I can recall on how AT&T, T-Mobile, Cingular behaved back in 2000 to 2007 (prior to iPhone1) and yet unbranded phones are aplenty.  Unlocking is common, and debranding was a thing to do.


EDIT: Quote mark boundaries wrong, edited to show where quote started and ended

[rsjsouza]

...
Have you guys all forgotten what the pre-iPhone days of mobile carriers were like, in particular in USA? ATT (the old one on TDMA), Sprint and Verizon used nearly-proprietary hardware. (And remember Nextel, which literally used an entire proprietary mobile network standard?) Cingular and T-Mo were already GSM but locked down everything. Every carrier loaded custom firmware onto their devices to plaster their proprietary BS apps everywhere, defacing even excellent hardware. (I had an otherwise lovely Sony-Ericsson phone that Cingular had stolen two useful buttons from, hard-mapping them to useless carrier apps instead of the useful functions those buttons normally had.)

Then Apple came along and convinced Cingular to agree to have zero control over the handset software and apps. I cannot overstate enough how much of a game changer this was. And then all the other carriers had to agree to the same thing because they wanted to sell the iPhone, too. The entire smartphone industry benefited immensely from Apple dedtroying the carriers’ stronghold on handset software. Apple is the company that turned the carriers into the “dumb pipes” they should be.

Our recollection is not the same, perhaps because regional/national differences.  I don't recall Apple being influential to the phone market at all in the early days.

Being a heavy user of Palms and Treos and their very large software catalog downloadable directly from the internet, my recollection is identical as yours. Regarding phone locking, I also recall the unlocking was already quite ubiquitous in the early 2000s. The introduction of Apple perhaps influenced more dramatically the regular user due to the convenience of the app and music stores. Besides, their first product with the UI and the capacitive touchscreen was quite good. Despite this, I was still very fond of a keyboard and a former Graffitti heavy user, but these do not appeal to anyone these days.

[tooki]

...
Have you guys all forgotten what the pre-iPhone days of mobile carriers were like, in particular in USA? ATT (the old one on TDMA), Sprint and Verizon used nearly-proprietary hardware. (And remember Nextel, which literally used an entire proprietary mobile network standard?) Cingular and T-Mo were already GSM but locked down everything. Every carrier loaded custom firmware onto their devices to plaster their proprietary BS apps everywhere, defacing even excellent hardware. (I had an otherwise lovely Sony-Ericsson phone that Cingular had stolen two useful buttons from, hard-mapping them to useless carrier apps instead of the useful functions those buttons normally had.)

Then Apple came along and convinced Cingular to agree to have zero control over the handset software and apps. I cannot overstate enough how much of a game changer this was. And then all the other carriers had to agree to the same thing because they wanted to sell the iPhone, too. The entire smartphone industry benefited immensely from Apple dedtroying the carriers’ stronghold on handset software. Apple is the company that turned the carriers into the “dumb pipes” they should be.

Our recollection is not the same, perhaps because regional/national differences.  I don't recall Apple being influential to the phone market at all in the early days.

At the time Cingular was Cingular (early 2000, Cingular not yet acquired by AT&T), I needed both T-Mobile and Cingular as my regular carrier.  I had coverage with T-Mobile at home (and no Cingular), and Cingular at work (but no T-Mobile).  I had T-Mobile cheap flip phone that was unlocked and can use Cingular and other alien SIMs.  It was also very simple to get Cingular phones unlocked to use T-Mobile and other alien SIM also.  So those phones were entirely carrier independent, I used them in the USA, Europe, and Asia.  The carrier has nothing to say about it and they had no control over it.  For a carrier branded phone, they can refuse to give you the unlock code, but you can always get a phone (like the Moto Razr) that is factory unlocked.

Then in 2004, I switch over to Treo 650.  I have factory-unlocked ones that swap SIMs (T-Mobile, Cingular, other alien SIMs) without distinction.  It just works.  I have unlocked Cingular-branded Treo 650 and they can use alien SIM without distinction.  I later "debranded" the Cingular Treo 650 to run pure Treo 650 firmware also without problem.  The only Cingular thing about them (after debranding) was just the different color scheme the phone have (Cingular ones are lighter grey and a Cingular label metallic color frame around the TFT screen).  Again, entirely carrier independent.  I even have an after market dual-SIM kit that allowed you to cut your two SIMs and fit it into the same SIM tray - but both SIMs are not active at the same time, you select which SIM to use with a Treo 650 App that came with the kit.

That was way before Apple even got into the phone market. Apple iPhone 1 was introduced in 2007.

I was addicted to debranding.  I was still using my Treo as my main phone, but I have my two Zenfone 2e (AT&T only) phones unlocked (not factory unlocked, but with unlock code) and debranded so they run ASUS software with nothing AT&T there.  They are like Asus Zenfone 2 (ZE500CL) but with less memory.  I ended up sticking with my Treo650 until carriers moved to sunset 2G/2.5G phones to 3G only.

So, carrier has no control with factory unlocked phones prior to Apple even got into the market.  They had no influence I can recall on how AT&T, T-Mobile, Cingular behaved back in 2000 to 2007 (prior to iPhone1) and yet unbranded phones are aplenty.  Unlocking is common, and debranding was a thing to do.


EDIT: Quote mark boundaries wrong, edited to show where quote started and ended

The GSM carriers grudgingly allowed you to bring your own devices, but they didn’t really like it. Almost all customers bought a phone under contract, complete with carrier-spoiled firmware, and that was no accident.

Here’s what Wired had to say in 2008 about Apple’s influence: https://www.wired.com/2008/01/ff-iphone/

But as important as the iPhone has been to the fortunes of Apple and AT&T, its real impact is on the structure of the $11 billion-a-year US mobile phone industry. For decades, wireless carriers have treated manufacturers like serfs, using access to their networks as leverage to dictate what phones will get made, how much they will cost, and what features will be available on them. Handsets were viewed largely as cheap, disposable lures, massively subsidized to snare subscribers and lock them into using the carriers' proprietary services. But the iPhone upsets that balance of power. Carriers are learning that the right phone—even a pricey one—can win customers and bring in revenue. Now, in the pursuit of an Apple-like contract, every manufacturer is racing to create a phone that consumers will love, instead of one that the carriers approve of. "The iPhone is already changing the way carriers and manufacturers behave," says Michael Olson, a securities analyst at Piper Jaffray.

What's more, the Cingular team could see that the wireless business model had to change. The carriers had become accustomed to treating their networks as precious resources, and handsets as worthless commodities. This strategy had served them well. By subsidizing the purchase of cheap phones, carriers made it easier for new customers to sign up—and get roped into long-term contracts that ensured a reliable revenue stream. But wireless access was no longer a luxury; it had become a necessity. The greatest challenge facing the carriers wasn't finding brand-new consumers but stealing them from one another. Simply bribing customers with cheap handsets wasn't going to work.

[Rick Law]

We are mixing up the time frame we are discussing, so we are having disagreement here.

iPhone's 2007 introduction no doubt accelerated the mobile market and mobile standardization in the USA after it's introduction.  But in my view,  iPhone is the benefactor pre-existing inter-operability and standardization that was already ubiquitous and vibrant.

I personally think Europe in 1990/1991 adopted (and rolled out) the GSM standard was the real big game changer in cell phones standardization and interoperability.  That drove GSM to become the global standard dominating everywhere else except the USA.  The USA's remaining big non-GSM was Verizon's CDMA.  The rest of the non-GSM carriers pretty much became small niche players or joined the GSM bang wagon.

The other big factor was China.  The domination of GSM globally and China's entry into the market drove the consolidation and standardization as well.  Well before iPhone (2007), one can pick up an unlocked phone far cheaper than even carrier-branded phones, and both were made in China anyway.  The only interoperability issues was frequency bands, and the CDMA's relatively big isolated island that was Verizon.  The small niche players remained small.

Standardization is a good thing but has it's very bad side...  Now our choices are far more limited - Android, or iPhone.  Well, perhaps I should include KaiOS, but version 2.5 integrated Google Assist and Google Map.  So while they are not Android, they surely have became part-Android.

An imaginary conversation one afternoon:

Tom: Hey, Dick, this investment fund looks like a pyramid scheme.
Dick: Pyramid or not pyramid, I don't have the funds.  So no need to go there yet.
...Before Harry can talk, something in his pocket interjected...
Phone: Most well known pyramids are in Egypt, do you want to know more about Egypt?  I also know a lot of discount flights and FUN tours for Egypt.  If you want to go there, say "tour" or "flights".
Harry: Shut the f*** up, phone; or I will throw you out the freaking window again.
Phone: This is the ...(brief pause)... 5th time ...(brief pause)... you are acting irrationally and exceeded government guide lines.  Your ability to invoke payment will be suspended for ...(brief pause)...  3 days ...(brief pause)...

[tooki]

We are mixing up the time frame we are discussing, so we are having disagreement here.

iPhone's 2007 introduction no doubt accelerated the mobile market and mobile standardization in the USA after it's introduction.  But in my view,  iPhone is the benefactor pre-existing inter-operability and standardization that was already ubiquitous and vibrant.

I personally think Europe in 1990/1991 adopted (and rolled out) the GSM standard was the real big game changer in cell phones standardization and interoperability.  That drove GSM to become the global standard dominating everywhere else except the USA.  The USA's remaining big non-GSM was Verizon's CDMA.  The rest of the non-GSM carriers pretty much became small niche players or joined the GSM bang wagon.

The other big factor was China.  The domination of GSM globally and China's entry into the market drove the consolidation and standardization as well.  Well before iPhone (2007), one can pick up an unlocked phone far cheaper than even carrier-branded phones, and both were made in China anyway.  The only interoperability issues was frequency bands, and the CDMA's relatively big isolated island that was Verizon.  The small niche players remained small.

Standardization is a good thing but has it's very bad side...  Now our choices are far more limited - Android, or iPhone.  Well, perhaps I should include KaiOS, but version 2.5 integrated Google Assist and Google Map.  So while they are not Android, they surely have became part-Android.

An imaginary conversation one afternoon:

Tom: Hey, Dick, this investment fund looks like a pyramid scheme.
Dick: Pyramid or not pyramid, I don't have the funds.  So no need to go there yet.
...Before Harry can talk, something in his pocket interjected...
Phone: Most well known pyramids are in Egypt, do you want to know more about Egypt?  I also know a lot of discount flights and FUN tours for Egypt.  If you want to go there, say "tour" or "flights".
Harry: Shut the f*** up, phone; or I will throw you out the freaking window again.
Phone: This is the ...(brief pause)... 5th time ...(brief pause)... you are acting irrationally and exceeded government guide lines.  Your ability to invoke payment will be suspended for ...(brief pause)...  3 days ...(brief pause)...

Standardization of the network standards wasn’t the issue to which I was referring. That was a done deal (except for Nextel) long before. (VZW and Spring on CDMA, ATT and T-Mo on GSM. The 90s in USA were littered with many non-GSM phone standards, such as “old” ATT’s TDMA and Nextel’s proprietary thing.)

Before the iPhone, the carriers sold nearly all handsets, and dictated to the handset makers what their phones could and couldn’t do. (Again: almost nobody brought their own devices.)

Apple broke this model by giving the networks no control over the device software. I told you what happened. I told you when. I’ve provided independent proof of this. Why are you still confused about what I am (and what I am not!) saying?! 

[Rick Law]

...
Standardization of the network standards wasn’t the issue to which I was referring. That was a done deal (except for Nextel) long before. (VZW and Spring on CDMA, ATT and T-Mo on GSM. The 90s in USA were littered with many non-GSM phone standards, such as “old” ATT’s TDMA and Nextel’s proprietary thing.)

Before the iPhone, the carriers sold nearly all handsets, and dictated to the handset makers what their phones could and couldn’t do. (Again: almost nobody brought their own devices.)

Apple broke this model by giving the networks no control over the device software. I told you what happened. I told you when. I’ve provided independent proof of this. Why are you still confused about what I am (and what I am not!) saying?! 

Our recollections really differ.  But, not a difference worth more ink.  I'll just accept that we recollect differently.

[bson]

I personally think Europe in 1990/1991 adopted (and rolled out) the GSM standard was the real big game changer in cell phones standardization and interoperability.  That drove GSM to become the global standard dominating everywhere else except the USA.  The USA's remaining big non-GSM was Verizon's CDMA.  The rest of the non-GSM carriers pretty much became small niche players or joined the GSM bang wagon.

That's not nearly an accurate history. 

Metro-PCS in the U.S. was a service to target millions of users in urban areas.  TDMA couldn't scale to these proportions; European GSM evolved from local standards like NMT and was designed for a very small set of high-paying customers to have mobile phone access, usually with a car phone.  TDMA was focused on broad geographic coverage, not a large number of customers.  CDMA was adopted in the U.S. and Asia exactly because of the different markets: cheap service to millions of urban users rather than an expensive luxury for politicians and CEOs to always be available. By 3G is was clear TDMA was a dead end, and CDMA was adopted for GSM.  It was also clear the U.S. and Asian market prediction was bulls-eye spot on, and the old GSM model couldn't meet it.  But instead of simply adopting existing CDMA systems, a completely new system was invented to prevent U.S. and Asian equipment vendors from dominating the European market.  At that time state phone companies were often still closely tied into manufacturing.  So an incompatible standard, neither technical better or worse, was invented with entirely new patent coverage to guarantee European telcos had a chance to remain in the game.  Americans and Asians played along too, since that was their only avenue to enter the European market.  European telcos would have been too far behind without a fresh start, and the market would quickly have been dominated by Americans and Asians.  It's not CDMA that was incompatible with 3GPP and 4G, it was GSM that was the gratuitously incompatible system.

Operator lock-in has little to nothing to do with network compatibility.  That's just subscriber access control, which operates at a higher layer.